Non-fouling liquid level control

ABSTRACT

A non-fouling liquid level detector and control especially for a sealed system likely to have iron particle contaminants. The device employs a float projecting above the liquid level and bearing above the liquid level a unmagnetized ferromagnetic tell-tale. A magnetic field is generated by a magnet positioned outside the sealed system. The magnetic field extends around the float and tell-tale through a magnetically permeable partition comprising a wall of the sealed system that is positioned between the magnet and the float. The float position is monitored by a magnetic field sensor such as a Hall Effect device positioned adjacent the magnet, outside the sealed system. The sensor responds to the movement of the tell-tale. The output of the sensor is employed to control the monitored liquid level.

PRIORITY

This patent application and the inventors hereof claim priority based onthe following Provisional Patent Applications

Serial 60/242,206 Filed Oct. 23, 2000

Serial 60/249,316 Filed Nov. 17, 2000

Serial 60/256,255 Filed Dec. 18, 2000

Serial 60/293,792 Filed May 25, 2001

BACKGROUND OF THE INVENTION Prior Art

A number of electronic oil level control systems for refrigerationcompressors have been in use in the past. U.S. Pat. No. 5,103,648discloses an optical system for monitoring and reacting to oil levelwithin a compressor.

U.S. Pat. No. 6,125,642 teaches an oil level control system employingthe complex permittivity of the oil compared with the permittivity ofthe vapor refrigerant environment.

U.S. Pat. No. 5,911,289 (Clive Waller) discloses an oil level monitoringand control systems based on the use of a float residing on the pool oilsurface. The float is attached to one end of a pivoting rod. The rodbears at its other end a permanent magnet that moves in a reversedirection from the float level. The pivoting float, rod and magnet arewithin the refrigerant/oil circuit. At times the magnet is immersedwithin the oil pool. The position of the magnet is monitored external ofthe refrigerant/oil circuit thru a non-ferrous wall built into thedevice adjacent which the magnet moves. A Hall-Effect magnetic fielddetector is positioned external of the refrigerant/oil circuit andadjacent the magnetically permeable non-ferrous wall. As the float armpivots, the arcuate motion of the permanent magnet adjacent thepermeable wall causes the Hall-Effect device to respond the change inthe strength of the magnetic field associated with the movement of themagnet and thereby activate control valves or alarm signals as required.

BACKGROUND Problems

All these control devices and systems based on their use have exhibitedcontrol problems and false alarms generated during the oil foamingconditions frequently arising during periods of operation immediatelyafter compressor startup or during periods of refrigerant liquidfloodback into the oil pool whose level was the control objective.

New non-ozone damaging refrigerants are frequently of thehydrofluorocarbon type (HFC). The manufacturers of these HFCrefrigerants require the use of a miscible lubricant such as polyolester(POE). POE acts as a cleaning agent of all the sludge in the system andentrains this dirt with the POE as it returns to the compressor. Notonly do the metal particles, accompanying and part of the sludge,accumulate on magnets immersed in the oil, the sludge accumulation canalso affect the optical level sensing devices by fostering the formationof surface foam that fools the optical detectors. Foam also occurs whenrefrigerant dissolved in the oil then boils out of the oil on a sharpreduction of pressure that occurs at starting and other times. Surfacefoam affects both optical and wave-based sensing systems.

Operational problems with the Waller construction have been reported.These problems have been primarily caused by the weight of very finemetal and iron wear particles in the oil that are attracted to themagnet on one end of the float. As the weight of the Waller magnetgradually increases because of the accretion of the wear particles, theposition of the magnet is biased downward, thereby falsely indicating ahigher oil level than truly exists, thus failing to cause entry ofmake-up oil or failing to actuate an alarm, even when the true oil levelhas dropped to the danger point.

The invention disclosed herein overcomes the faults of the Waller deviceand the several optical based level sensors and controllers.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a liquid level sensing andcontrol device that is unaffected by magnetic and metallic particles.

It is a further object to provide such a device that does not require amagnet positioned within the liquid whose level is sensed.

It is a further object to provide such a device that employs the HallEffect principle to detect the position of a float positioned to followlevel changes of the monitored liquid and to employ as tell-tale anunmagnetized ferromagnetic tell-tale mounted on the float.

It is a further object to provide such a device that employs a floatthat moves in a straight-line motion in conformance with the change inthe level of the monitored liquid.

It is a further object to secure the straight line float motion byproviding a float whose motion is constrained by at least onesubstantially straight guide.

It is a further object to secure the straight line motion by employing afloat whose motion is constrained by two substantially straight guides.

It is a further object to provide such straight line motion by employingsubstantially straight guide members that traverse the float.

It is a further object to facilitate the performance of a Hall Effectsensor by employing a magnet positioned substantially adjacent the HallEffect sensor.

It is a further object to employ a magnet in the shape of a ring shapedto allow the Hall Effect sensor to occupy a position within the centralarea of the ring.

It is a further object to moderate the effect of the magnet by the useof a ferromagnetic bridge between the magnet and the working area.

It is a further object to moderate the effect of the ring magnet byemploying a ferromagnetic pole-piece positioned in contact with the ringmagnet.

It is a further object to moderate the effect of the magnet by employinga ring-shaped pole-piece positioned in substantial contact with the ringmagnet.

It is further object to moderate the effect of the magnet by utilizingan electromagnet and moderating the current flow through its windings.

SUMMARY OF THE INVENTION

For a closed system, a level sensing and controlling device for a liquidhaving a rising and falling level, the device including a float ofnon-magnetic material, a magnetic couple comprising a magnetized partand an unmagnetized part, the float having attached thereto one part ofthe magnetic couple, at least one guide constraining the float and itsattached part to move in a straight substantially vertical line with therise and fall of the liquid level, a magnetically permeable partitionsubstantially adjacent the float for separating the interior of theclosed system from the exterior, a Hall Effect sensor positionedsubstantially adjacent the partition exterior and the other part of thecouple positioned substantially adjacent the Hall Effect sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

All of the embodiments disclosed include a magnetically permeablepartition positioned between a magnetic or ferromagnetic tell-tale and aHall Effect sensor.

FIG. 1 shows an outline of a hermetic compressor of the type to whichthe invention could be applied.

FIG. 2 shows an outline of the device enclosure mounted in two positionson a hermetic compressor.

FIG. 3 shows two views of an embodiment of the invention having atell-take side mounted on a float within the sealed system and aside-mounted sensor outside the sealed system.

FIG. 4 shows two views of one version of a preferred embodiment having afloat with a top mounted ferromagnetic tell-tale sensing a level withinthe system and a Hall Effect sensor positioned outside the systempositioned above the tell-tale.

FIG. 5 shows in several views an embodiment of the invention where apermanent magnet is mounted on top of the float as a tell-tale and theHall Effect sensor is positioned above the float outside the sealedsystem or on bottom and the Hall Effect sensor is beneath the float atposition 48 a.

FIG. 6 shows a modification of the embodiment of FIG. 4 where magnet isoutside the sealed circuit and a ferromagnetic bridge is employed torefine and adjust the effect of the permanent magnet on thefloat-mounted tell-tale.

FIG. 7 illustrates an embodiment of the invention employing a ringshaped magnet positioned above and outside the sealed system and aferromagnetic ring-shaped magneto-bridge provided to control the effectof the permanent magnet.

DETAILED DESCRIPTION OF THE INVENTION General Description of theEnvironment

While this invention was developed primarily for use in the lubricatingoil sumps or reservoirs of compressors in sealed air conditioning andrefrigeration systems, the device is perfectly suited for monitoring acritical liquid level within any closed or sealed environment includingchemical, petroleum, pharmaceutical, aeronautical, aerospace andnuclear.

The device employs a Hall Effect part or Hall Effect sensor to detectthe position of a float having a density lower than the density of theliquid monitored. The float bears a ferromagnetic tell-tale. The termferromagnetic is employed throughout this description to mean either aferrous but non-magnetized material capable of distorting or changing amagnetic field or a non-ferrous material or device having the capabilityof distorting or changing a magnetic field. The term magnet is employedto denote either a permanent magnet or an electromagnet. The floatassembly includes one or more rods or guides or both for ensuring thatthe float traverses a substantially straight up and down path that isperpendicular to the liquid level surface and conforming to the changein oil or liquid level monitored.

The oil level controller also includes electronic switches to operate asolenoid valve positioned within an oil feed conduit for supplyingadditional oil to the float monitored reservoir or sump when necessaryand to provide a relay output to either cause the compressor to turn offor produce an alarm. The electronic circuit can also provide time delaysprior to making oil feed or compressor off decisions. The oil feedconduit, solenoid valve and electronic logic devices are shown asrudimentary elements only, since they are all well known.

A typical operating sequence is as follows:

(1) The oil level while the compressor is running is maintained between½ and ⅓ distance of the diameter of the sightglass.

(2) When the oil level falls to ⅓ sightglass, it is detected by the oillevel sensing circuit and, after a 10 second delay, the electroniccircuit switches on a solenoid valve to feed oil into the compressorcrankcase from a reservoir.

(3) If the oil feed causes the crankcase oil level to reach the ½sightglass level as detected by the oil level sensing circuit, the oilwill feed for 10 more seconds and the circuit will switch the solenoidvalve to its closed position.

(4) If the oil feed fails to bring the crankcase oil level up to the ksightglass level in 120 seconds, thereby indicating failure of thesolenoid valve or lack of oil in the reservoir, the output relay willclose to cause the compressor to turn off or produce an alarm indicationor both actions can be produced from a secondary relay.

While no specific circuitry is shown associated with the Hall Effectsensor to accomplish these actions, the design of such circuitry is wellknown and readily available from the purveyors of the Hall Effect sensoror others.

The Hall Effect was discovered by Edwin Hall in 1879. He discovered thatwhen a conductor (or semiconductor) with current flowing in onedirection was moved in a direction perpendicular to a magnetic field, avoltage was generated whose potential was at right angles to the currentpath. Solid state devices are widely available in the form of smallpackaged integrated circuits (IC) that employ the Hall Effect to actuateintegral switches on movement of a magnetic field relative to the ICpackage.

The voltage output of the Hall Effect sensor increases as the magneticfield strength increases. As the float with its ferromagnetic tell-talemoves up, the magnetic field strength increases as the extraferromagnetic material of the tell-tale is added to the magnetic field,thereby causing the Hall Effect sensor to increase its voltage output tothe electronic circuit.

Conversely, as the float moves down, the voltage output of the HallEffect sensor is reduced. At some preset minimum voltage, the electroniccircuit energizes an oil feed solenoid valve to increase the oil levelin the chamber or performs some other desired function.

While the applications illustrated for the Hall Effect (HE) device inthe advertisements and application literature uniformly show the devicereacting to the approach or passing of a magnet, in the applicationdisclosed herein, the magnet is positioned in fixed relation to the HallEffect device and the change in magnetic field is induced by motion ofan unmagnetized ferromagnetic element whereby the magnetic fieldprojected by the adjacent magnet is sufficiently distorted by theapproach or passing of a non-magnetized ferromagnetic part to actuatethe Hall switch. The source of magnetism could be a permanent magnet oran electromagnet.

Referring now to FIG. 1 there is shown a refrigeration compressor of thetype to which the instant invention can be applied. The compressor iscontained within shell 20 formed usually of welded steel sheet. Theinlet gas or suction connection 22 and compressed gas or dischargeconnection 24 are both positioned on the side of shell 20. Within thecompressor, at the bottom of shell 20 is a pool of oil 27 having asurface 26. While very small compressors of the type employed indomestic refrigerators and window air conditioner do not have any way toobserve the oil level 26 within shell 20, larger compressors intendedfor use in built-up systems have boss 28 welded to the exterior of shell20 and sight glass assembly 29 comprising a metal exterior and glasswindow 30 fused to the metal exterior. The assembly 29 is held in placeagainst boss 28 by bolts 32 with an intermediate gasket or O-ring (notshown) to prevent leakage.

FIG. 1A is a cross-section of a portion of compressor shell 20, boss 28and sightglass 29, illustrating the relationship of the parts to thecompressor shell and the oil pool 27 and oil level 29.

Referring now to FIGS. 2 and 2A, there is shown in FIG. 2 a front viewof the compressor which appears the same as that of FIG. 1, except thereis shown an outline of vertical enclosure 34 that is constructed andarranged to hold and secure parts of the invention, whereby the level 26of oil pool 27 is monitored and if necessary, an electric signal sent toa valve (not shown) to open and supply oil to the pool, when needed, orto ring an alarm or even to open an valve to allow an excess quantity ofoil to be removed from pool 27. Vertical enclosure 34 is directed to theconstructions of FIGS. 4, 5, 6 and 7 where a ferromagnetic part ispositioned above the oil level and above the top of the float and theHall Effect sensor is positioned above the float. The orientation ofenclosure 36 is directed to the construction of FIG. 3 where the HallEffect sensor is positioned immediately horizontally adjacent the oillevel 26 and positioned to detect motion of a ferromagnetic partpositioned on the float at or near the oil level.

Referring to FIG. 2A there is shown a cross-section 2A—2A of theconstruction of FIG. 2 wherein is shown space 37 in which the operativeparts of the float mechanism are positioned. The mechanical installationprocedure of enclosure 34 or 36 involves (after removal of therefrigerant charge, simply removing sight glass assembly 29, positioningthe invention-containing enclosure 34 or 36 over boss 28 andreinstalling sight glass 29, with longer bolts, if necessary.

FIG. 3 provides a side view (horizontal elevation) of enclosure 36positioned in place on compressor boss 28. Sight glass 29 which is shownin FIG. 3A has been removed in FIG. 3 for improved clarity. It must benoted that the oil 27, the float 38 and other interior parts are allpositioned within a sealed system containing a pressurized refrigerantsuch as hydrochlorofluorocarbon HCFC-22 or hydrofluorocarbon blendR-410A and the omission of sightglass in this view is for clarity only.The interior of boss 28 and enclosure 34 or 36 encloses space 37 aboveoil pool 27 with oil level 26 defined as the surface of the oil pool 27.Floating in oil pool 27 is float 38. Float 38 is constructed to have anaverage density less than the density of the oil 27 so that it willfloat on the oil. In the disclosed embodiment the floatation part of thefloat or float material is formed of solid polyethylene or polypropylene‘plastic’ having specific gravities in the range of 0.90 to 0.92. Methylpentene copolymer, offered under the tradename TPX, has a lower specificgravity, in the range of 0.83 and provides a solid float material moresuitable for less dense lubricants such as alkyl benzene that are widelyemployed in close coupled systems with some hydrofluorocarbonrefrigerants such as R134a or R-410A. While foamed plastics can offereven lower densities, the higher pressures exhibited by some modernrefrigerants suggest that simple foamed float construction may haveshort service life. Further, hollow floats assembled of metals such assteel or stainless steel and formed into a hollow structure shaped tofit and allow the desired motion within the allowed space may worksatisfactorily, they are costly to manufacture and exhibit the risk offailure by implosion or leaking. Molded plastics have the additionaladvantage of being able to be readily formed into more complex shapes tofit into space restricted environments. Molded foamed graphite is also asuitable float material.

To better insure properly low density of float without prejudicing itsphysical integrity under high pressures, two internal constructions areshown in FIG. 3A. There, the cross-section of float 38 has been dividedinto portions 38 a and 38 b where 38 a exhibits a float having a uniformhomogeneous interior and 38 b exhibits an internal construction formedof a mixture or composite of moldable plastic having the samecomposition as in 38 a plus embedded particles of one or more lowdensity solid materials such as exploded silica, foamed glass or glassspheres or glass micro spheres.

Float 38 has a substantially straight line motion following verticallypositioned guide rod 40 that traverses float 38. Positioned on andfastened to the side of float 38 is ferromagnetic part 44. While thepart 44 is positioned below the oil level, in other embodiments of theinvention the part 44 is positioned on the side of float 38 but abovethe oil level 26 at position A or even on top of the float 38 atpositioned B. It should be clearly emphasized that the ferromagneticpart 44 is not magnetized and therefore is incapable of attracting anyparticles of materials that may be entrained within oil pool 27 orfloating on surface 26. Such particles being of types or materials thatmight or would be attracted to iron magnets or electromagnets or magnetsof other types.

Hall Effect sensor 48 is positioned in apparatus chamber 46 that isoutside the sealed pressurized system but within enclosure 36. The HallEffect sensor is located and secured within equipment chamber 46,approximately at the normal oil level 26, and on or adjacent to themagnetically permeable partition 39 that serves to isolate the contentsof the sealed system from the Hall Effect sensor and from the outsideatmosphere and the equipment chamber 46. Slight positional deviations ofthe Hall Effect sensor may be necessary to comport with expected oillevel ranges and Hall

Effect device sensitivities and other variables. Positioned ‘atop’ HallEffect sensor 48 is a magnet 50. Atop in this context means that themagnet is positioned so that the Hall Effect sensor is between themagnet and the tell-tale 44. While magnet 50 is shown positioned indirect contact with Hall Effect sensor 48, a spacer or other means maybe employed to move the magnet away from Hall Effect sensor 48 in orderto adjust the sensitivity of the combination to provide desired responseof the Hall Effect sensor to motion of ferromagnetic tell-tale 44 and toadjust for initial variations in the magnetic strength of magnet 50.

The soft ferromagnetic tell-tale 44 does not hold permanent magnetismbut affects the reluctance of a magnetic field. As the float changesposition with a change in oil level, the tell-tale 44 positioned on thefloat alters the magnetic field sensed by the Hall Effect sensor andchanges its electronic signal output, thereby allowing the associatedswitches or actuate or stop the desired activity. Solenoid valve 65 isconnected to a reservoir of oil, via conduit 68 and to the body of oil27 by conduit 67. Solenoid valve 65 is actuated by a connection 66between it and Hall Effect sensor 48.

In another embodiment of the invention, magnet 50 is an electromagnetand is activated by a direct current. In an embodiment of thisconstruction, provisions are provided for periodically stopping the flowof electric current to the electromagnet. The advantage of thisconstruction is that when the current is turned off the magnet isdeenergized, its magnetic field collapses and any magnetic particlesthat might have been attracted to the interior of magnetically permeablepartition 39, drop to the bottom of the oil pool 27 where they areunlikely to do harm, by contrast with their harmful potential whilecirculating with the oil. In another embodiment, means are provided forperiodically reversing the flow of direct current to the electromagnet.

FIG. 3A is a section of FIG. 3 along section line 3A—3A. This top viewof float 38 teaches that it is formed with a substantially cylindricalportion having a centrally located hole within which guide rod 40 ispositioned. Guide bars 42 are molded into float 38 and serve to keep thefloat and ferromagnetic tell-tale aligned with the Hall Effect sensorassembly that is positioned within equipment chamber 46 on theunpressurized side of magnetically permeable wall 39. FIG. 3A displayssight glass assembly 29 (omitted from FIG. 3) in its proper position.

While the usual function of an Hall Effect sensor is to respond tochanges in the location of a moving magnet, in this embodiment themagnet is positioned in fixed relationship to the Hall Effect sensor andthe actuation of the Hall Effect sensor is secured through movement ofthe unmagnetized tell-tale ferromagnetic part 44, mounted to and movingwith float 38. The Hall Effect device 48 is caused to respond, not bymotion of the fixed magnet 50 with respect to the Hall Effect sensor butby changes in distortion of the magnetic field affecting the Hall Effectsensor by movement of non-magnetized ferromagnetic tell-tale 44 withinthe magnetic field generated by magnet 50. The great advantage of suchan arrangement is that the magnet is outside the sealed system.Therefore any magnetic particles that might collect on the interiorsurface of partition 39 within float chamber 37, cannot bias themovement of float 38 in any way. Such bias has been a major fault ofprior art devices that teach the location of the magnet on or in weightrelationship with the float. In that construction accumulation of ironparticles on the magnet bias it in a direction causing erroneousresponse of the Hall Effect sensor to liquid level.

In FIG. 4 there is shown a side elevation of oil sight glass boss 20that is part of compressor shell 20. Sight glass 29, whose positionrelative to the assembly is shown in FIG. 4A, has been omitted from FIG.4 for clarity. Also, the hatch signifying the presence of oil pool 27has been omitted from the float chambers in FIGS. 4 and 4A for clarity,though it must be understood that the pool of oil 27 resides below theindicated oil level 26. Float and electronics enclosure 34, havingvertical format, and showing electronics chamber 46 and float chamber 37is shown positioned on boss 28. Hall Effect sensor 48 is positionedabove float chamber 37 and is separated from it by magneticallypermeable partition 39. Magnet 50 is positioned on the opposite side ofHall Effect sensor 48 from wall 39. Magnet 50 is separated or spacedfrom Hall Effect sensor 48 by spacer 51. Typically, spacer 51 is formedof a magnetically permeable material whose thickness is selected toprovide a magnetic field whose structure or intensity will be mosteffectively changed by the approach or recession of tell-tale 44 withrespect to Hall Effect sensor 48. Within float chamber 37 is positionedfloat 52 having a truncated circular shape in this frontal view. Thecircular shape is modified by planar truncations at top and bottomparallel chords. Float 52 rides on and is guided into a substantiallystraight vertical motion by two guide rods 54. A ferromagnetic tell-tale44 is positioned on and fastened to the top planar chordal surface offloat 52 where an up or down motion of float 52 causes tell-tale 44 toapproach or recede from magnetically permeable partition 39, on theother side of which is positioned Hall Effect sensor 48. Magnet 50 ispositioned outside the pressurized compartment and within chamber 37.Magnet 50 is secured on the opposite side of Hall Effect sensor 48 frompartition 39 and from tell-tale 44 positioned on float 52. As float 52rises and falls, ferromagnetic tell-tale 44 distorts the magnetic fieldsurrounding magnet 50 and extending into float chamber 37, therebyaffecting the intensity of the magnetic field traversing Hall Effectsensor 48 and causing it to actuate a solid state or mechanical switchat a position in the float's travel that can be determined by test. Aadjustment of the ‘trip-point’ for actuation of a switch is secured bymoving magnet 50 and/or Hall Effect sensor 48 away from or closer topartition 39. One these positions are determined, they are mechanicallyfixed. The positions of Hall Effect sensor 48 and magnet 50 are intendedto be initially adjusted by the manufacturer to provide correctoperation. Therefore, depiction in the drawings of those elements alwaysin contact with partition 39 is not intended to be determining. Itshould be noted that the magnetically permeably partition 39 could bepositioned substantially parallel with the level 26 but underneath thefloat in contact with the liquid 27. In that case the tell-tale 44 wouldbe positioned at 44 b (FIG. 7) and Hall Effect sensor 48 would be at thebottom of the boss 28. Under certain operating conditions where theliquid surface at level 26 is highly agitated or subject to foaming, thesensitivity of sensor 48 to motion of the tell-tale 44 or 44 b would beincreased, since the condition of the fluid between the tell-tale 44 andthe magnetically permeable partition 39 would remain substantiallyconstant.

Non-straight sectional line 4A—4A in FIG. 4 is positioned to allow thesimplest and clearest view of the construction of the assembly in FIG.4A.

Referring now to FIG. 4A there is shown compressor shell 20 with oilsight glass boss 28 attached thereto. Sightglass 29 has been temporarilyremoved and enclosure 34 positioned and sight glass assembly 29 replacedand bolted securely to boss 28, thereby providing float chamber 37 indirect communication with the interior of compressor shell 20 and theoil pool 27 residing therein. Guide holes within float 52 foraccommodating guide pin 54 in other embodiments are replaced by grooves55 formed in the sides of float 52 thereby simplifying the moldingprocess.

FIGS. 5 and 5A are substantially similar to FIGS. 4 and 4A describedabove, with the exception that tell-tale 56, that is secured to theupper planar chordal surface of float 52, is a permanent magnet.Permanent magnet 56 approaches and recedes from Hall Effect sensor 48 asfloat 52 rises and falls with the level 26 of oil pool 27, therebychanging the intensity of the magnetic field traversing Hall Effectsensor 48 and causing the Hall Effect sensor 48 to open or close anelectrical circuit in response thereto. In an alternate embodiment HallEffect sensor is positioned at 48 a beneath the float. FIG. 5B simplyshows, in a plan cross-section 5B—5B, the Hall Effect sensor positionedwithin compartment 46.

In FIG. 6 there is shown a float assembly substantially the same as thatshown and described in FIG. 4. However, in FIGS. 6 and 6A, Hall Effectsensor 48 is shown positioned slightly off-center of the vertical axisof float 52 and permanent magnet 50 is positioned alongside the HallEffect sensor but spaced from it. Magnetic bridge 58 is formed of aferromagnetic material and is positioned on magnet 50 and extendingwholly or partly over Hall Effect sensor 48 to provide an extension ofthe magnetic field generated by magnet 50, over the Hall Effect sensor48. The thickness and positioning of Hall Effect sensor 48 and magnet 50and magnetic bridge 58 must be adjusted to secure the most effectivereaction of Hall Effect sensor 48 to movement of ferromagnetic telltale44.

FIG. 7 shows a float 52 and ferromagnetic tell-tale 44 mounted on thefloat that is substantially identical to those shown and described inFIGS. 4 and 6. It should be noted that, while the position of tell-tale44 or 56 has been shown and described having a position on top of float52, other positions 44 a and 44 b for the tell-tale are also effectiveand, in certain case or environments desirable. In position 44 a, thetell-tale is embedded within float 52, thereby providing the tell-taleprotection against corrosion by the oil or fluid. In position 44 b thetelltale is positioned on and attached to the bottom of float 52,thereby providing a greater distance between Hall Effect sensor 48 andthe tell-tale.

Referring now to both FIGS. 7 and 7A, apparatus chamber 46 has beenmodified by providing a cylindrical chamber for Hall Effect sensor 48.The chamber and the Hall Effect sensor 48 are positioned adjacentmagnetically permeable partition 39. A second cylindrical chamber,coaxial with the cylindrical chamber holding Hall Effect sensor 48, isformed above the sensor chamber. Within the second chamber arepositioned ferromagnetic ring 62 and, substantially adjacent ring 62 andfurther from he sensor 48 is positioned ring magnet 64. Ferromagneticring 62 provides a moderating influence on the magnetic field generatedby ring magnet 64, thereby providing a magnetic field that is sharplyaffected by motion of the tell-tale 44, 44 a or 44 b towards or awayfrom Hall Effect sensor 48, thereby providing an effective measure ofthe position of float 52 and oil level 26.

It should be noted that the term ferromagnetic must also be applicableto non ferrous materials such a certain ceramics that have magnetic orferromagnetic qualities and to materials such as Cobalt, Nickel and toalloys and ceramics containing these materials as metals, oxides or inorganic and inorganic compositions that exhibit the characteristic ofchanging or distorting a magnetic field within which these materials arepositioned.

As used herein, density is the mass of a substance per unit volume ofthat substance; specific gravity of a substance is the density of thatsubstance divided by the density of water at defined conditions. Averagedensity of a construct is the mass of the construct divided by itsvolume.

From the foregoing description, it can be seen that the presentinvention comprises an advanced level detection and control assembly forliquids or oils within a pressurized environment. It will be appreciatedby those skilled in the art that changes could be made to theembodiments described in the foregoing description without departingfrom the broad inventive concept thereof. It is understood, therefore,that this invention is not limited to the particular embodiment orembodiments disclosed, but is intended to cover all modifications whichare within the scope and spirit of the invention as defined by theappended claims, as well as by each of the elements enumerated andequivalents thereof.

We claim:
 1. A level control device for liquid having a density, theliquid having a changeable level and a surface corresponding to thelevel, an enclosure having an inside and an outside, the liquid beingcontained inside the enclosure, a magnetically permeable partitionseparating the enclosure inside from the enclosure outside, said devicefurther comprising: float means for moving in response to a change inliquid level, guide means for causing the float to move in a straightline path substantially perpendicular to the liquid surface, magnetmeans for establishing a magnetic field, said magnet means beingpositioned outside the enclosure, means associated with the float meansfor affecting the magnetic field, magnetic field sensor means employinga Hall Effect for responding to the magnetic field as affected by thefloat means, said magnetic field sensor means being positioned outsidethe enclosure, and further providing that said magnetic field sensormeans is positioned substantially adjacent said permeable partition andthe magnet means is positioned substantially adjacent said magneticfield sensor means, but spaced from said partition.
 2. A liquid levelcontrol device as recited in claim 1 further providing that the magnetmeans, while substantially adjacent the magnetic field sensor means, isspaced from said magnetic field sensor means.
 3. A liquid level controldevice as recited in claim 2 where there is a magnetically permeablespacer between the magnet means and the magnetic field sensor means. 4.A liquid level control device as recited in claim 2 where there is aferromagnetic spacer between the magnet means and the magnetic fieldsensor means.
 5. A level control device for liquid having a density, theliquid being contained within an enclosure interior, the liquid having achangeable level and a surface corresponding to the level, said devicecomprising: magnet means positioned outside the enclosure forestablishing a magnetic field, float means for moving in response to achange in liquid level and unmagnetized means associated with the floatmeans for affecting the magnetic field, guide means for causing thefloat to move in a straight line path substantially perpendicular to theliquid surface, and magnetic field sensor means positioned outside theenclosure for responding to the magnetic field as affected by the floatmeans.
 6. A liquid level control device as recited in claim 5 andfurther providing a magnetically permeable partition separating themagnetic field sensor means from the enclosure interior.
 7. A liquidlevel control device as recited in claim 6 further providing that themagnetically permeable partition is substantially parallel to the liquidsurface.
 8. A liquid level control device as recited in claim 7 wherethe liquid surface interfaces with vapor above the surface and where thepartition is in contact with the vapor.
 9. A liquid level control deviceas recited in claim 7 where the partition is in contact with the liquid.10. A liquid level control device as recited in claim 7 and furtherproviding Hall Effect magnetic field sensor means and that said magnetmeans and said magnetic field sensor means are both positioned on asingle planar surface that is substantially parallel to the liquidsurface, and that said magnetic field sensor means and said magnet meansare separated by a distance.
 11. A liquid level control device asrecited in claim 10, further providing a ferromagnetic bridge positionedin contact with said magnet means and extending towards, but separatedfrom, said magnetic field sensor means.
 12. A liquid level controldevice as recited in claim 7, further providing a substantiallycylindrical first cavity within the permeable partition within whichfirst cavity said magnetic field sensor means is positioned, the firstcavity having a diameter and a central axis substantially perpendicularto the liquid surface, and a second cavity coaxial with the first cavityand substantially adjacent to the first cavity, said second cavityhaving a larger diameter than said first cavity and further providingmagnet means comprising a ring magnet positioned within said secondcavity.
 13. A liquid level control device as recited in claim 12,further providing a ferromagnetic ring positioned in the second cavitybetween the ring magnet and the sensor.
 14. A level control device forliquid having a density, the liquid being contained within an enclosureinterior, the liquid having a changeable level and a surfacecorresponding to the level, said device comprising magnet means forestablishing a magnetic field, float means for moving in response to achange in liquid level and means associated with the float means foraffecting the magnetic field, further providing that the float meanscomprises methyl pentene copolymer float material and associatedmagnetic field affecting means and that the float means has an averagedensity less than the density of the liquid, guide means for causing thefloat to move in a straight line path substantially perpendicular to theliquid surface, and magnetic field sensor means positioned outside theenclosure for responding to the magnetic field as affected by the floatmeans.
 15. A level control device for liquid having a density, theliquid being contained within an enclosure interior, the liquid having achangeable level, a surface corresponding to the level, said devicecomprising: magnet means for establishing a magnetic field, float meansfor moving in response to a change in liquid level, said float meanscomprising float material and means associated with the float means foraffecting the magnetic field, and further providing that the float meanshas an average density less than the density of the liquid and furtherproviding that said float material comprises matrix means for providingan average float means density lower than the liquid density, saidmatrix means comprising moldable plastic material having a densitygreater than the liquid and material of a lower density embeddedtherein, whereby the average density of the float means is lower thanthe liquid density, and guide means for causing the float means to movein a straight line path substantially perpendicular to the liquidsurface, and magnetic field sensor means positioned outside theenclosure for responding to the magnetic field as affected by the floatmeans.
 16. A level control device for liquid as recited in claim 15,further providing that the material of lower density embedded in theplastic is hollow glass microspheres.
 17. A level control device asrecited in claim 15 where the embedded material of lower density is agas.
 18. A level control device as recited in claim 14 further providingthat the float material is in the form of a matrix comprising methylpentene copolymer with embedded glass microspheres.
 19. A level controldevice for liquid having a density, the liquid being contained within anenclosure interior, the liquid having a changeable level and a surfacecorresponding to the level, said device comprising: magnet means forestablishing a magnetic field, float means for moving in response to achange in liquid level and means associated with the float means foraffecting the magnetic field, further providing that the float meanscomprises methyl pentene copolymer float material and associatedmagnetic field affecting means and that the float means has an averagedensity less than the density of the liquid, and magnetic field sensormeans positioned outside the enclosure for responding to the magneticfield as affected by the float means.
 20. A level control device asrecited in claim 19 further providing that the float material is in theform of a matrix comprising methyl pentene copolymer with embedded glassmicrospheres.
 21. A level control device for liquid having a density,the liquid being contained within an enclosure interior, the liquidhaving a changeable level and a surface corresponding to the level, saiddevice comprising: magnetically permeable partition means for separatingthe enclosure interior from the enclosure outside, magnet means forestablishing a magnetic field, said magnet means being positionedoutside the enclosure, float means for moving in response to a change inliquid level and unmagnetized ferromagnetic means associated with thefloat means for affecting said magnetic field, and Hall Effect sensormeans for responding to the magnetic field as affected by the floatmeans, said Hall Effect means being positioned outside the enclosure.22. A level control device as recited in claim 21, further providingthat the unmagnetized ferromagnetic means associated with the floatmeans for affecting the magnetic field includes material selected fromthe group consisting of iron, cobalt, nickel and alloys or ceramicsthereof.
 23. A level control device as recited in claim 21 furtherproviding that said magnet means is positioned outside the enclosure andabove said float means.
 24. A level control device as recited in claim23 where said Hall Effect magnetic field sensor means is positionedoutside the enclosure and above said float means.